Many hand-held devices contain multiple components that may require power sources that are capable of providing multiple voltage levels. For example, hand-held measuring equipment may contain processing logic that requires a different voltage level than, for example, a liquid crystal display (LCD) unit. LCDs, which are used in many hand-held device applications including wristwatches, toys and games, and hand-held test and measurement equipment, require a compact, high voltage output (as compared to for example, processing logic) power supply. LCDs offer an efficient way of presenting information to a user and are common in the above mentioned devices.
Modern LCDs offer many features that just a few years ago were unavailable, and as a result, require ever increasing sources of voltage in order to operate. In the past power supplies have employed oscillators, or tank circuits, to provide the voltage levels required to drive LCDs. Other LCD voltage sources use boost regulators or additional windings on special transformers. These sources have fixed outputs that require the use of post regulators to set contrast in the LCD. Unfortunately however, power supplies using these technologies to drive LCDs are expensive and use a large number of parts. Furthermore, as power and processing demands are ever increasing for hand-held devices, battery life for devices containing LCDs continue to drop, thus creating a need in the industry for a new efficient power source that is capable of supplying the high voltage levels demanded by modern LCDs, while minimizing power consumption and component cost.